EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: anvoice on May 18, 2020, 08:51:17 am
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I'd like to make a quarter wavelength T/R switch that will work at roughly 0.5-1MHz, to switch between transmitter and receiver signal. The simplest choice seems to be to use an equivalent representation for the roughly 50 to 100 meters of cable that I'd need for this. Such a representation requires at least one inductor, which I calculated to be about 8-16uH, from H = 50 / (2 * pi * f) for a 50 Ohm coaxial cable. It also needs two capacitors which I calculate to be approximately 3-6nF according to the formula: C = 1 / (2 x pi x f x Xc), where if I understand correctly Xc is 50.
My problem is I don't know how close the inductor and capacitors need to be to the calculated values. After all, while I can wind my own inductor, the capacitors will be fixed, and due to tolerances will not even be exactly their nominal value. Do I need to use inductance and capacitance values that are exactly as calculated by the formula for the switch to work properly? Or will approximate values suffice? If so, how close do they need to be?